Process chamber for etching low k and other dielectric films

ABSTRACT

Methods and process chambers for etching of low-k and other dielectric films are described. For example, a method includes modifying portions of the low-k dielectric layer with a plasma process. The modified portions of the low-k dielectric layer are etched selectively over a mask layer and unmodified portions of the low-k dielectric layer. Etch chambers having multiple chamber regions for alternately generating distinct plasmas are described. In embodiments, a first charge coupled plasma source is provided to generate an ion flux to a workpiece in one operational mode, while a secondary plasma source is provided to provide reactive species flux without significant ion flux to the workpiece in another operational mode. A controller operates to cycle the operational modes repeatedly over time to remove a desired cumulative amount of the dielectric material.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/552,183 filed on Oct. 27, 2011 titled “Process Chamber for EtchingLow K and Other Dielectric Films,” the content of which is herebyincorporated by reference in its entirety for all purposes.

TECHNICAL FIELD

Embodiments of the present invention pertain to the field ofmicroelectronic device processing and, in particular, to plasma etchingof low-k dielectric films.

DESCRIPTION OF RELATED ART

In semiconductor manufacturing, a low-k dielectric is a material with asmall dielectric constant relative to silicon dioxide. Low-k dielectricmaterial implementation is one of several strategies used to allowcontinued scaling of microelectronic devices. In digital circuits,insulating dielectrics separate the conducting parts (e.g., wireinterconnects and transistors) from one another. As components havescaled and transistors have moved closer together, the insulatingdielectrics have thinned to the point where charge build-up andcrosstalk adversely affect the performance of the device. Replacing thesilicon dioxide with a low-k dielectric of the same thickness reducesparasitic capacitance, enabling faster switching speeds and lower heatdissipation.

However, significant improvements are needed in the evolution of low-kdielectric processing technology because processing of such films,particularly the etching of such films, has been found to damage and/orrender the materials unstable or otherwise unsuitable for devicefabrication.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are illustrated by way of example,and not limitation, in the figures of the accompanying drawings inwhich:

FIG. 1 is a flow diagram illustrating a multi-operational mode etchprocess for etching a low-k dielectric film with a single plasma etchchamber, in accordance with an embodiment of the invention;

FIG. 2 is a flow diagram further illustrating how an etch chamber mayoperate in the multiple modes utilized by the etch process illustratedin FIG. 1, in accordance with an embodiment;

FIGS. 3A, 3B, 3C, 3D, 3E, and 3F illustrate cross-sectional viewsrepresenting the effects of the method of multi-operational mode etchprocess 100 on an exemplary workpiece exposed to the process, inaccordance with an embodiment of the present invention;

FIG. 4, is a plan view of a multi-chambered processing platform that maybe configured to include one or more etch chambers to perform themulti-operational mode etch process illustrated in FIG. 1, in accordancewith an embodiment;

FIG. 5A depicts a cutout perspective view of a dual zone showerheadwhich may be utilized in an etch chamber to perform themulti-operational mode etch process illustrated in FIG. 1, in accordancewith an embodiment;

FIG. 5B illustrates an enlarged portion of the cutout perspective viewof FIG. 5A, in accordance with embodiments of the present invention;

FIG. 6A illustrates a cross-sectional view of an etch chamber configuredto perform the modification operation of the etch process illustrated inFIG. 1, in accordance with an embodiment;

FIG. 6B illustrates a cross-sectional view of an etch chamber configuredto perform the etching operation of the etch process illustrated in FIG.1, in accordance with an embodiment;

FIG. 6C illustrates a cross-sectional view of an etch chamber configuredto perform the deposition operation of the etch process illustrated inFIG. 1, in accordance with an embodiment;

FIG. 7 illustrates a cross-sectional view of an etch chamber configuredto perform the modification operation of the etch process illustrated inFIG. 1, in accordance with an embodiment;

FIG. 8A illustrates a cross-sectional view of an etch chamber configuredto perform the modification operation of the etch process illustrated inFIG. 1, in accordance with an embodiment;

FIG. 8B illustrates a cross-sectional view of an etch chamber configuredto perform the etching operation of the etch process illustrated in FIG.1, in accordance with an embodiment;

FIG. 8C illustrates a cross-sectional view of an etch chamber configuredto perform the deposition operation of the etch process illustrated inFIG. 1, in accordance with an embodiment;

FIG. 9A illustrates a cross-sectional view of an etch chamber configuredto perform the modification operation of the etch process illustrated inFIG. 1, in accordance with an embodiment;

FIG. 9B illustrates a cross-sectional view of an etch chamber configuredto perform the etching operation of the etch process illustrated in FIG.1, in accordance with an embodiment;

FIG. 9C illustrates a cross-sectional view of an etch chamber configuredto perform the deposition operation of the etch process illustrated inFIG. 1, in accordance with an embodiment; and

FIG. 10 illustrates a cross-sectional view of an etch chamber configuredto perform the various operations illustrated in FIG. 1, in accordancewith an embodiment.

DETAILED DESCRIPTION

Generally, embodiments of the plasma etch methods described hereinleverage damage mechanisms to etch low-k (and other dielectric)materials and leave a remainder of the etched film in good condition.Embodiments of the plasma etch methods described herein cyclicallyperform at least two separate plasma-based operations in-vaccuo (i.e.,without breaking vacuum), and preferably in a same chamber for greatestthroughput advantage. During one of these operations, an anisotropic(directional) plasma modifies the bulk structure and/or composition of aportion of the dielectric film being etched to be more like silicondioxide (SiO₂), or a silicon sub-oxide (SiO_(x)). This film modificationoperation may be conceptualized as controllably and selectively damaginga portion of the dielectric film with the first plasma conditions.During a second of these operations, an isotropic (non-directional)condition removes the modified film portion (having the modifiedstructure or composition) selectively over the underlying dielectricfilm having the bulk properties. These operations may be performedsequentially and repeatedly to achieve any desired cumulative amount offilm removal (i.e., to achieve a desired etch depth). Through thisseparation of a bulk film etch into two distinct operations oroperational modes, the design of the plasma conditions, as well as thedesign of the etch chamber to provide those conditions, has asignificantly greater degree of freedom and/or larger process window.

Separation of the dielectric film etch process into at least these twoseparate operational modes also provides a level of control over theetch parameters that enables etching an anisotropic profile into thelow-k or other dielectric film with advantageously little modificationof the dielectric film composition in regions adjacent to the etchedfeature (e.g., sidewalls are not negatively impacted through exposure tothe plasma etch). An important source of this precise control arisesfrom the isotropic etch condition being highly chemical in nature, andas such, providing very high selectivity between the underlyingdielectric having bulk properties deviating from that of SiO₂ (e.g.,incorporating carbon to some degree). While high selectivity between twomaterial compositions is often leveraged to stop an etch after a firstmaterial layer is consumed (e.g., in a multi-material deposited filmstack as a means to terminate an etch of a layer having an etchablecomposition with an underlying etch stop layer having a non-etchablecomposition), the techniques herein incrementally etch through a bulkfilm with an etch process that is a high selectivity to the bulk filmitself.

In embodiments, the multi-operational mode etch processes are entirelyfluorocarbon-free. While conventional dielectric etches rely on CFpolymer deposited onto the sidewalls of the etched dielectric layer toachieve etch anisotropy, the methods herein achieve etch anisotropy byway of the anisotropy of the film modification process (mode) incombination with the high selectivity of the film etch process (mode).Avoidance of the typically fluorocarbon-based (C_(x)F_(y)-based) etchprocess and the attendant CF polymer renders etched dielectric surfacesrelatively cleaner of any passivation polymer. As such, post-etchtreatment (PET) by plasma or other means which may damage dielectrics(e.g., through oxidation of carbon species in the film) may be avoided.

A more detailed description of the etching method, how such a method maybe performed in a single chamber, and chamber hardware adapted toperform embodiments of such an etching method is now provided. Turningfirst to description of the etching method, FIG. 1 is a flow diagramillustrating a multi-operational mode etch process 100 for etching alow-k dielectric film with a single plasma etch chamber, in accordancewith an embodiment of the invention. FIGS. 3A-3F illustratecross-sectional views representing the effects of the method ofmulti-operational mode etch process 100 on an exemplary workpieceexposed to the process, in accordance with an embodiment of the presentinvention.

Beginning at operation 105, a workpiece is loaded in a plasma processingchamber. While the workpiece may generally take any form, in theillustrative embodiment presented in FIG. 2A, the workpiece includes asubstrate 302 upon which a dielectric to be etched is disposed. Thesubstrate 302 may be of any material suitable to withstand a fabricationprocess and serves as a basis for which microelectronic device layersmay be disposed and/or formed, such as those for IC, optical, solar,MEMs, or similarly micro/nano fabricated devices. In accordance with anembodiment of the present invention, substrate 302 is composed of agroup IV-based material such as, but not limited to, crystallinesilicon, germanium or silicon/germanium. In a specific embodiment,substrate 302 is a monocrystalline silicon substrate. In anotherembodiment, substrate 302 is composed of a III-V material. In anotherembodiment, a plurality of active devices is disposed within the regiondemarked as substrate 302.

The workpiece further includes exposed dielectric to be etched. In theexemplary embodiments illustrated in FIGS. 1 and 3A-3F, the exposeddielectric is a low-k material, but more generally may be any materialwhich is not silicon dioxide and is modifiable into a material more likesilicon oxide (SiO_(x)) by the mechanisms described herein. In theexemplary embodiment illustrated in FIG. 3A, the low-k dielectric layer304 has a permittivity less than that of silicon dioxide, e.g., lessthan approximately 3.9. In a further embodiment, the low-k dielectriclayer 304 is a material such as, but not limited to, a fluorine-dopedsilicon dioxide, a carbon-doped silicon dioxide, a porous silicondioxide, a porous carbon-doped silicon dioxide, a spin-on silicone basedpolymeric dielectric, or a spin-on organic polymeric dielectric. Inaccordance with one illustrative embodiment, the low-k dielectric layer304 is a porous SiCOH layer having a bulk dielectric constant of lessthan 2.7.

While the multi-operational mode etch process 100 is applicable tounmasked etches, for example in etches where underlying topography isutilized to form features in a low-k dielectric layer (e.g., a low-kspacer etch), in the illustrative embodiment the low-k dielectric layer304 is masked (e.g., for a via or trench etch). As illustrated in FIG.3A, the mask layer 306 is a photoresist layer or hardmask layer disposedover a portion of the low-k dielectric layer 304. The photoresist may beany known in the art (e.g., 193, EUV, etc.). Similarly, where the masklayer 306 is a hardmask, any material known in the art capable ofproviding a desired selectivity to a SiO_(x) etch process may beutilized. Exemplary materials include: amorphous carbon (e.g., APR®),nitrides of silicon or metals (e.g., titanium or tantalum), carbides ofsilicon or metal, etc.

Returning to FIG. 1, at operation 110, exposed portions of the workpieceare bombarded with an ion flux to modify the properties of the exposedmaterial layer, and more particularly reduce carbon content in a topthickness of a low-k film. The ion flux is preferably anisotropic suchthat regions underlying a mask are not exposed to the flux. The ion fluxmay be of one or more types of atomic or molecular species having a lowion energy. As such, in one advantageous embodiment, the species is tomechanically mill off constituents in the low-k material (e.g.,knock-off methyl groups) rather than chemically react with them andtherefore the ion flux is to originate from a source gas havingrelatively low chemical reactivity with the target constituent.Exemplary ionic species include helium ions, neon ions, xenon ions,nitrogen ions, or argon ions with Ar+ being preferred as having a lowionization potential (e.g., 2-4 eV) such that very low plasma DC biasescan be provided to reduce energy levels of the ion flux. Electropositivediluents, like neon and helium may also be added to an argon environmentto further tune the ion flux energy. Process pressures areadvantageously below 10 mTorr for more directionality and moreadvantageously below 5 mTorr. Low RF powers on the order of 50 W to 100W, depending on the ionization potential of the feed gas, have beenfound advantageous for modifying a low-k dielectric film by knocking outcarbon species from the silicon-oxide matrix.

FIG. 3B illustrates the effect of operation 110 on a workpiece. Asshown, the ion flux 307 forms modified portions 308 of the low-kdielectric layer 304. In an embodiment, the modified portions 308 arecarbon-depleted, and therefore SiO_(x) enriched, relative to the bulk,unmodified portions of the low-k dielectric layer 304. Film density andmorphology of the modified portions 308 may also be altered related tothe low-k dielectric layer 304. For example, the modified portions 308may be densified or otherwise mechanically damaged (e.g., roughened) bythe ion bombardment during operation 110. Depending on the ion flux, thedepth of the modified portions 308 may amount to 50 Å or less.

Returning to FIG. 1, at operation 120, a dry etch process is employed toremove the SiO_(x)-enriched modified portion of the low-k dielectriclayer selectively over the underlying bulk (or unmodified portion 304Bof the low-k dielectric layer 304 in FIG. 3C). The etching operation 120is to be considered atomic layer etching or molecular level etching(MLE) since the modified portion removed is on the order of thedimension of the molecular constituents in the low-k dielectric film. Inone embodiment, operation 120 entails a plasma generated from at leastnitrogen trifluoride (NF₃) and a hydrogen source, such as ammonia (NH₃)or water vapor (H₂O) to generate reactive etch species NH₄F and/orNH₄F.HF. In a further embodiment, water vapor (H₂O) is provided alongwith the NF₃ and NH₃ to further enhance the SiO_(x) etch rate atoperation 120. Nonreactive gases (e.g., He) may also be utilized duringoperation 120.

In another embodiment, the etch process 100 employs a siconi-typeetching technique, which is further described in more detail in U.S.patent application Ser. No. 12/620,806, commonly assigned, entails a twostep mechanism that is to be performed during the operation 120. In thisembodiment, water vapor (H₂O) and a thin solid silicate etch byproduct(e.g., (NH₄)₂SiF₆) is formed at a lower first workpiece temperature(e.g., 30° C.) and the silicate is then sublimed from the workpiece at ahigher second workpiece temperature (e.g., 100° C.). In certainembodiments however, for example where a higher etch rate is desired,the siconi etching is performed at a fixed elevated workpiecetemperature. Without the additional overhead of cycling the substratetemperature, the etch process 100 may be cycled more rapidly for ahigher etch rate. Preferably, the fixed workpiece temperature atoperation 120 is between about 80° C. and 100° C. While highertemperatures are possible for hardmask and unmasked embodiments ofmethod 100, the maximum fixed workpiece temperature at operation 120 forembodiments employing photoresist is below approximately 120° C. so asto avoid reticulation. In certain embodiments, both operations 110 and120 are performed at the fixed elevated temperature to avoid anyoverhead relating to cycling the workpiece temperature.

Returning to FIG. 1, an etch process controller determines if an etchprocess termination criteria is met subsequent to the completion ofoperation 120. The etch process termination criteria may be based on aprocess duration, endpoint signal (optical or otherwise), or the like.If the etch process termination criteria is met, the process 100 iscomplete and the workpiece is unloaded from the chamber 150. If the etchprocess termination criteria is not yet met, a subsequent iteration isinitiated by returning to operation 110.

For a further embodiment, a low-temp conformal silicon-based dielectriclayer is deposited over the workpiece at operation 130. The depositionoperation 130 may be periodically performed during the etch process 100,for example to combat any profile undercut or bow that results from themodification operation 110 not being perfectly anisotropic as a functionof the ion flux not being an ideally collision-less mode of transport.As illustrated in FIG. 1, the deposition operation 130 is performed onlyon the condition an etch cycle count threshold has been met where eachetch cycle entails a single performance of both operations 110 and 120.As such, the deposition operation 130 may be performed with every etchcycle (etch cycle count threshold of 1) or at some lesser rate (etchcycle count threshold greater than 1) for a “multi-X” cyclic processinterleaving the etch and deposition operations together at apredetermined ratio or duty cycle.

As further shown in FIG. 3D, the deposition operation 130 forms aprotection layer 312 which is formed at least on the sidewalls of thebulk low-k dielectric 304B exposed by the etch operation 120. Thethickness of the protection layer 312 may vary widely depending on thefrequency at which operation 130 is performed relative to the etchoperation 120. Generally, the deposition operation 130 entails aconformal deposition process to ensure sidewall coverage. Inembodiments, the conformal deposition process is low temperature (e.g.,below 130° C.) so as to preserve the overlying mask material (e.g.,photoresist). In an embodiment, the protecting layer 312 is a silicondioxide. However, in one advantageous embodiment, the protecting layer312 is a carbon-doped silicon oxide. Deposition of a carbon doped layermay advantageously increase resistance of the protection layer 130 tothe etch operation 120 such that a subsequent iteration through the etchoperation 120 will not completely remove the protection layer 130,particularly from the sidewalls of the trench 310. In still anotherembodiment, the protecting layer 312 is a silicon nitride. For carbondoped and nitride embodiments where the protection layer 130 offersselectivity to the etch operation 120, the etch cycle count thresholdmay be made higher for a greater portion of the process 100 expended onetching, and an increase in the overall low-k dielectric etch rate.

Depending on the embodiment, any commonly known silicon precursor may beemployed at operation 130, such as, but not limited to silicontetrafluoride (SiF₄), silicon tetrachloride (SiCl₄), silane (SiH₄), orany commonly known silicon-containing carbonized precursor, such as, butnot limited to, octamethylcyclotetrasiloxane (OMCTS),tetramethyl-disiloxane (TMDSO), tetramethylcyclotetrasiloxane (TMCTS),tetramethyl-diethoxyl-disiloxane (TMDDSO), dimethyl-dimethoxyl-silane(DMDMS). In further embodiments, where the protection layer is to benitride, precursors, such as, but not limited to trisillylamine (TSA)and disillylamine (DSA) may be utilized. Any of these sources may bereacted with an oxygen radical source such as, but not limited to,oxygen (O₂), ozone (O₃), carbon dioxide (CO₂), or water (H₂O) in a PECVDprocess.

Following operation 130, a subsequent iteration is performed byreturning to operation 110. In this manner, the etch front isincrementally advanced through the target film, as further shown inFIGS. 3E and 3F, to form a progressively deeper trench 210B.

FIG. 2 is a flow diagram further illustrating how an etch chamber mayoperate in the multiple modes of the etch process 100. Method 200 beginswith receiving the workpiece in the chamber at operation 205. The ionmilling plasma is energized in a first region of the chamber disposedbelow a showerhead closest to the workpiece. An RF source provides a DCbias potential on the workpiece to generate the ion flux describedelsewhere herein for the modification operation 110. In embodiments, theRF source is capacitively coupled through a pedestal or chuck upon whichthe workpiece is supported to generate a plasma in the first chamberregion directly over the workpiece. In one such embodiment, thecapacitively coupled plasma (CCP) is launched from the chuck (i.e.,chuck is RF driven) and the showerhead closest to the workpiece providesthe RF return path (i.e., as anode).

During operation 320, a SiO etching plasma is energized in a secondregion of the chamber to minimize, or avoid, biasing the workpiece in amanner that would induce ion flux to the workpiece. In one embodiment,to render the etching operation 320 highly chemical in nature, thesecond chamber region is disposed above the showerhead closest to theworkpiece and therefore relatively more remote from the workpiece thanthe ion milling plasma generated during operation 310. In an embodiment,the pedestal or chuck is not RF powered during operation 320 to minimizeworkpiece bias potential. Remote and/or soft ionization techniques areemployed at operation 320 to form the reactive species for the etchingoperation 120 described elsewhere herein without forming a significantbias potential on the workpiece. In one such embodiment, a second CCP islaunched to or from the showerhead closest to the workpiece from or toan electrode disposed on a side opposite the showerhead from the wafer(e.g., from or to an electrode above the showerhead closest to theworkpiece). In another embodiment, a DC discharge is employed as asource of electrons for soft ionization during the etching operation120. In an alternative embodiment, a remote plasma source (RPS) isemployed to form the plasma in the second region of the chamber. Instill another embodiment, an inductively coupled plasma (ICP) isemployed to form the plasma in the second region of the chamber. Etchchamber hardware configurations for each of these embodiments is furtherdescribed elsewhere herein.

For embodiments which deposit a protection layer (e.g., operation 130 inFIG. 1), an oxidizing plasma is generated in the remote second region ofthe chamber and the silicon (and carbon) containing precursor isintroduced into the chamber, for example into the first chamber region,to react with oxidizing species transported to the workpiece. As such, afirst region and first operational mode of a plasma etch chamber may beutilized for modifying a partial thickness of a low-k dielectric filmand a second region and second operational mode of the plasma etchchamber may be utilized for etching the modified thickness of the low-kdielectric film. The second region may further be operated in a thirdoperational mode to deposit a protection layer.

For embodiments which utilize a siconi-type process, the two stages ofthe siconi-type etch may further entail two different plasmas launchedand generated in the different regions of the etching chamber. Forexample, both the first and second chamber regions may be utilized toperform the siconi-type process, or the second chamber region and athird chamber region may be employed to perform the siconi-type process.

As shown in FIG. 4, one or more low-k etch chambers 405, configured asdescribed elsewhere herein, are coupled to an integrated platform toform a multi-chambered processing system. One or more of the embodimentsdescribed for the multi-operational mode etch process 100 may beperformed by each of the low-k etch chamber 405 in the multi-chamberedsystem depicted in FIG. 4. Referring to FIG. 4, the multi-chamberedprocessing platform 400, may be any platform known in the art that iscapable of adaptively controlling a plurality of process modulessimultaneously. Exemplary embodiments include an Opus™ AdvantEdge™system, a Producer™ system, or a Centura™ system, all commerciallyavailable from Applied Materials, Inc. of Santa Clara, Calif.

The processing platform 400 may further include an integrated metrology(IM) chamber 425 to provide control signals to allow adaptive control ofany of the etch processes described herein. The IM chamber 425 mayinclude any metrology commonly known in the art to measure various filmproperties, such as thickness, roughness, composition, and may furtherbe capable of characterizing grating parameters such as criticaldimensions (CD), sidewall angle (SWA), feature height (HT) under vacuumin an automated manner. As further depicted in FIG. 4, themulti-chambered processing platform 400 further includes load lockchambers 430 holding front opening unified pods (FOUPS) 435 and 445,coupled to the transfer chamber 401 having a robotic handler 450.

As the etch process performed in the low-k etch chambers 405 iterativelyprogresses with each cycle of the process 100, the low-k etch chambers405 may automatically cycle through the process 200, actuating relayscoupling an RF source to different electrode and/or operating distinctRF sources separately coupled to different electrodes to modulatebetween the operational modes. Such control over the low-k etch chambers405 may be provided by one or more controller 470. The controller 470may be one of any form of general-purpose data processing system thatcan be used in an industrial setting for controlling the varioussubprocessors and subcontrollers. Generally, the controller 470 includesa central processing unit (CPU) 472 in communication with a memory 473and an input/output (I/O) circuitry 474, among other common components.Software commands executed by the CPU 472, cause the multi-chamberedprocessing platform 400 to, for example, load a substrate into the low-ketch chamber 405, execute the multi-operation mode etch process 200, andunload the substrate from the low-k etch chamber 405. As known in theart, additional controllers of the robotic handler 450, or load lockchambers 430 is provided to manage integration of multiple low-k etchchambers 405.

One or more of the etch process chambers described in detail elsewhereherein may employ either a conventional showerhead or a “dual zone”showerhead (DZSH) for distribution and transport of fluids (reactivespecies, gases, etc.) to the workpiece. While a detailed description ofa DZSH may be found in U.S. Pat. No. 12/836,726, commonly assigned,FIGS. 5A and 5B illustrate some features of a DZSH 500 which may beadvantageously leveraged in particular embodiments of amulti-operational mode plasma etch chamber. FIG. 5A depicts a cutoutperspective view of the DZSH and FIG. 5B illustrates an enlarged portionof the cutout perspective view of FIG. 5A. As shown, the DZSH 500includes an upper manifold 510 with a plurality of first apertures 514and a lower manifold 530 having a plurality of second apertures 524. Afirst fluid flow, F₃ is through the showerhead via the apertures 514,second openings 524 in a center manifold, and second openings 534 in thebottom manifold 530 before entry into a processing region disposed belowthe DZSH 500. A second fluid flow F₄ is through a channel network to oneor more of the second gas channels 538 and delivery to the processingregion through apertures 542. The first fluid and the second fluid areisolated from one another in the DZSH until their respective deliveryinto the processing region. As such, the first fluid may be provided inan energized state (e.g., as a radical or ionic species) while thesecond fluid may be provided in an unreacted and/or unenergized state.

In an embodiment, a plasma etch chamber includes a plasma source coupledto a DZSH. In one embodiment, a “Siconi etch” source may be adapted froma Siconi etch/preclean chamber (commercially available from AppliedMaterials) to provide at least one plasma for the multiple operativemode chambers described herein. For example, the Siconi etch source mayprovide at least one of a first capacitive plasma source to implementthe ion milling operation (e.g., 110 of FIG. 1), and a secondcapacitively coupled plasma source to implement the etching operation(e.g., 120 of FIG. 1) and/or the optional deposition operation describedherein (e.g., 130 of FIG. 1).

FIGS. 6A, 6B and 6C illustrate cross-sectional views of an etch chamberconfigured into multiple modes (states) of operation, to perform each ofthe operations in the etch process 100 (FIG. 1), in accordance with anembodiment. Generally, the etch chamber 601 includes a firstcapacitively coupled plasma source to implement the ion millingoperation, a second capacitively coupled plasma source to implement theetching operation and to implement the optional deposition operation.FIG. 6A illustrates a cross-sectional view of an etch chamber 601configured to perform the modification operation 110 (FIG. 1), inaccordance with an embodiment. The etch chamber 601 has grounded chamberwalls 640 surrounding a chuck 650. In embodiments, the chuck 650 is anelectrostatic chuck (ESC) which clamps the workpiece 302 to a topsurface of the chuck 650 during processing, though other clampingmechanisms known in the art may also be utilized.

The chuck 650 includes an embedded heat exchanger coil 617. In theexemplary embodiment, the heat exchanger coil 617 includes one or moreheat transfer fluid channels through which heat transfer fluid, such asan ethylene glycol/water mix, Galden® or Fluorinert®, etc. may be passedto control the temperature of the chuck 650 and ultimately thetemperature of the workpiece 302.

The chuck 650 includes a mesh 649 coupled to a high voltage DC supply648 so that the mesh 649 may carry a DC bias potential to implement theelectrostatic clamping of the workpiece 302. The chuck 650 is coupled toa first RF power source and in one such embodiment, the mesh 649 iscoupled to the first RF power source so that both the DC voltage offsetand the RF voltage potentials are coupled across a thin dielectric layeron the top surface of the chuck 650. In the illustrative embodiment, thefirst RF power source includes a first and second RF generator 652, 653.The RF generators 652, 653 may operate at any industrial frequency knownin the art, however in the exemplary embodiment the RF generator 652operates at 60 MHz to provide advantageous directionality. Where asecond RF generator 653 is also provided, the exemplary frequency is 2MHz.

With the chuck 650 to be RF powered, an RF return path is provided by afirst showerhead 625. The first showerhead 625 is disposed above thechuck to distribute a first feed gas into a first chamber region 684defined by the first showerhead 625 and the chamber wall 640. As such,the chuck 650 and the first showerhead 625 form a first RF coupledelectrode pair to capacitively energize a first plasma 670 of the firstfeed gas within a first chamber region 684. A DC plasma bias (i.e., RFbias) resulting from capacitive coupling of the RF powered chuckgenerates an ion flux from the first plasma 670 to the workpiece 302(e.g., Ar ions where the first feed gas is Ar) to provide an ion millingplasma (e.g., operation 220 in FIG. 2). The first showerhead 625 may begrounded or alternately coupled to an RF source 628 RF having one ormore generators operable at a frequency other than that of the chuck 650(e.g., 13.56 MHz or 60 MH). In the illustrated embodiment the firstshowerhead 625 is selectably coupled to ground or the RF source 628through the relay 627 which may be automatically controlled during theetch process, for example by the controller 420.

As further illustrated in FIG. 6A, the etch chamber 601 includes a pumpstack capable of high throughput at low process pressures. Inembodiments, at least one turbo molecular pump 665, 666 is coupled tothe first chamber region 684 through a gate valve 660 and disposed belowthe chuck 650, opposite the first showerhead 625. The turbo molecularpump(s) 665, 666 may be any commercially available having suitablethroughput and more particularly is to be sized appropriately tomaintain process pressures below 10 mTorr and preferably below 5 mTorrat the desired flow rate of the first feed gas (e.g., 50 to 500 sccm ofAr). In the embodiment illustrated in FIG. 6A, the chuck 650 forms partof a pedestal which is centered between the two turbo pumps 665 and 666,however in alternate configurations chuck 650 may be on a pedestalcantilevered from the chamber wall 640 with a single turbo molecularpump having a center aligned with a center of the chuck 650.

Disposed above the first showerhead 625 is a second showerhead 610. Inone embodiment, during processing, the first feed gas source, forexample, Argon bottle 690 is coupled to a gas inlet 676, and the firstfeed gas flowed through a plurality of apertures 680 extending throughsecond showerhead 610, into the second chamber region 681, and through aplurality of apertures 682 extending through the first showerhead 625into the first chamber region 684. An additional flow distributor 615having apertures 678 may further distribute a first feed gas flow 616across the diameter of the etch chamber 601. In an alternate embodiment,the first feed gas is flowed directly into the first chamber region 684via apertures 683 which are isolated from the second chamber region 681(denoted by dashed line 623). For example, where the first showerhead isa DZSH, the apertures 683 correspond to apertures 542 in FIG. 5B.

FIG. 6B illustrates a cross-sectional view of the etch chamber 601reconfigured from the state illustrated in FIG. 6A to perform theetching operation 120 of FIG. 1, in accordance with an embodiment. Asshown, a secondary electrode 605 is disposed above the first showerhead625 with a second chamber region 681 there between. The secondaryelectrode 605 may further form a lid of the etch chamber 601. Thesecondary electrode 605 and the first showerhead 625 are electricallyisolated by a dielectric ring 620 and form a second RF coupled electrodepair to capacitively discharge a second plasma 691 of a second feed gaswithin the second chamber region 681. Advantageously, the second plasma691 does not provide a significant RF bias potential on the chuck 650.As illustrated in FIG. 6B, at least one electrode of the second RFcoupled electrode pair is coupled to an RF source for energizing anetching plasma at operation 220 in FIG. 2 (during the etching operation120 in FIG. 1). The secondary electrode 605 is electrically coupled tothe second showerhead 610. In a preferred embodiment, the firstshowerhead 625 is coupled to a ground plane or floating and may becoupled to ground through a relay 627 allowing the first showerhead 625to also be powered by the RF power source 628 during the ion millingmode of operation. Where the first showerhead 625 is grounded, an RFpower source 608, having one or more RF generators operating at 13.56MHz or 60 MHz for example is coupled to the secondary electrode 605through a relay 607 which will allow the secondary electrode 605 to alsobe grounded during other operational modes (e.g., during ion millingoperation 110), although the secondary electrode 605 may also be leftfloating if the first showerhead 625 is powered.

A second feed gas source, such as an NF₃ bottle 691, and a hydrogensource, such as NH₃ bottle 692, is coupled to the gas inlet 676. In thismode, the second feed gas flows through the second showerhead 610 and isenergized in the second chamber region 681. Reactive species (e.g.,NH₄F) then pass into the first chamber region 684 to react with theworkpiece 302. As further illustrated, for embodiments where the firstshowerhead 625 is a DZSH, one or more feed gases may be provided toreact with the reactive species generated by the second plasma 691. Inone such embodiment, a water source 693 may be coupled to the pluralityof apertures 683.

In an embodiment, the chuck 650 is movable along the distance ΔH₂ in adirection normal to the first showerhead 625. The chuck 650 is on anactuated mechanism surrounded by a bellows 655, or the like, to allowthe chuck 650 to move closer to or farther away from the firstshowerhead 625 as a means of controlling heat transfer between the chuck650 and the first showerhead 625 (which is at an elevated temperature of80° C.-150° C., or more). As such, a siconi etch process may beimplemented by moving the chuck 650 between first and secondpredetermined positions relative to the first showerhead 625.Alternatively, the chuck 650 includes a lifter to elevate the workpiece302 off a top surface of the chuck 650 by distance ΔH₁ to controlheating by the first showerhead 325 during the etch process. In otherembodiments, where the etch process is performed at a fixed temperature(e.g., ˜90-110° C.), chuck displacement mechanisms can be avoided.

The controller 420 is to alternately energize the first and secondplasmas 690 and 691 during the etching process by alternately poweringthe first and second RF coupled electrode pairs automatically.

FIG. 6C illustrates a cross-sectional view of the etch chamber 601reconfigured to perform the deposition operation 130 illustrated in FIG.1, in accordance with an embodiment. As shown, a third plasma 692 isgenerated in the second chamber region 681 by an RF discharge which maybe implemented in any of the manners described for the second plasma691. Where the first showerhead 625 is powered to generate the thirdplasma 692 during a deposition, the first showerhead 625 is isolatedfrom a grounded chamber wall 640 by a dielectric spacer 630 so as to beelectrically floating relative to the chamber wall. In the exemplaryembodiment, an oxidizer (O₂) feed gas source 694 is coupled to the gasinlet 676. In embodiments where the first showerhead 625 is a DZSH, anyof the silicon containing precursors described elsewhere herein (e.g.,OMCTS source 695) may be coupled into the first chamber region 684 toreact with reactive species passing through the first showerhead 625from the second plasma 692. Alternatively the silicon containingprecursor is also flowed through the gas inlet 676 along with theoxidizer.

FIG. 7 illustrates a cross-sectional view of an etch chamber 701configured to perform the modification operation 110, in accordance withan embodiment. As shown, the etch chamber 701 has a cantilevered chuck660 and a single turbo pump 665 having a center aligned with a center ofthe chuck 660. As further shown, the first showerhead 625 is groundedwhile the chuck 660 and secondary electrode 605 are both coupled to asame RF source via a relay 607 to alternate the driven electrode betweenthe chuck 660 and the secondary electrode 605 between the ion millingand etching operations 210 and 220 to implement the modification andetching operations 110 and 120, respectively, with the location of theplasma changing between the first chamber region 684 and the secondregion 681 in the manner described in the context of the chamber 601.Alternatively, RF source 608 may power the secondary electrodeindependently of the RF source powering the chuck 660 (e.g., one or moreof generators 652 and 653) with the location of the plasma changingbetween the first chamber region 684 and the second region 681 in themanner described in the context of the chamber 601.

FIG. 8A illustrates a cross-sectional view of an etch chamber 801configured to perform the modification operation 110 of the etch processillustrated in FIG. 1, in accordance with an embodiment. Generally, theetch chamber 801 comprises a first capacitively coupled plasma source toimplement the ion milling operation, a remote plasma source to implementthe etching operation, and optionally a second capacitively coupledplasma source to implement the deposition operation.

The etch chamber 801 includes a remote RF plasma source 823 disposedabove the first showerhead 625, opposite the chuck 660. In the ionmilling mode of operation, the etch chamber 801 provides a capacitivelycoupled first plasma 670 within the first chamber region 684substantially as described for the etch chamber 601. In the illustratedembodiment, the chuck 660 is coupled to a first RF power source (RFgenerators 652, and 653), and the first showerhead 625 is selectablycoupled, through relay 607B, to ground or a second RF power sourcecomprising one or more RF generators 608 operable at a frequency otherthan that of the first RF power source 652, 653. Where the firstshowerhead 625 is powered, the first showerhead 625 is isolated from agrounded chamber wall 640 by the dielectric spacer 630 so as to beelectrically floating relative to the chamber wall 640. For embodiments,wherein the first showerhead 625 is powered, the second showerhead 610and secondary electrode 605 may be electrically tied to the samepotential as the first showerhead 625.

FIG. 8B illustrates a cross-sectional view of the etch chamber 801reconfigured from that shown in FIG. 8A to perform the etching operation120 illustrated in FIG. 1, in accordance with an embodiment. As shown inFIG. 8B, in the etching mode of operation, the remote RF plasma source823 is to discharge a second plasma 693 of a second feed gas providedthrough the gas inlet 824. In one exemplary embodiment, the remote RFplasma source 823 and the first showerhead 625 are both coupled to asame RF power source 821 through a relay 607A controllable by thecontroller to alternately power the first plasma 670 and the remoteplasma 693. The remote plasma 693 is to be generated without placing asignificant RF bias potential on the chuck 660. In a preferredembodiment, the first showerhead 625 is grounded or floating. Secondfeed gases sources 691,692 (NF₃, NH₃) are coupled to the gas inlet 824with reactive species (e.g., NH₄F) then flowing through the firstshowerhead 625. Additional flow distribution may be provided with thesecond showerhead 610 and/or flow distributor 615, as describedelsewhere herein. In an embodiment where the first showerhead 625includes a DZSH, water vapor 693 may be provided through the apertures693 to react with reactive species entering the first chamber region 684through the apertures 682.

FIG. 8C illustrates a cross-sectional view of the etch chamber 801reconfigured from the states illustrated in FIGS. 8A and 8B to performthe deposition operation 130 illustrated in FIG. 1, in accordance withan embodiment. As shown in FIG. 8C, while in the deposition operationalmode, the chuck 660 is coupled to a first RF power source comprising oneor more RF generators 652, 653 which may be left unpowered (e.g.,floating). The first showerhead 625 is coupled to a second RF powersource comprising one or more RF generators 608 that may be at afrequency other than that of the RF generator 652 (e.g., 13.56 MHz).With the first showerhead 625 isolated from a grounded chamber wall 640by the dielectric spacer 630 and further isolated from the secondshowerhead 601 by the dielectric spacer 620, RF power to the firstshowerhead 625 is to generate a third plasma 692 (e.g., of an oxidizingsource gas such as O₂ 694) in the second chamber region 681. In oneexemplary embodiment, the first showerhead 625 and the remote RF plasmasource 823 are both coupled to a same RF power source 821 through arelay 607A controllable by the controller 470 to alternately power thethird plasma 692 and the remote plasma 693 between etch and deposition(e.g., operations 120 and 130 in FIG. 1, respectively).

The controller 420 is to alternately energize the first plasma 670 andremote plasma 693 during the etching process by alternately powering thetwo sources automatically. The controller 420 may similarly place thechamber 801 into the deposition mode.

FIG. 9A illustrates a cross-sectional view of an etch chamber 901configured to perform the modification operation 110 illustrated in FIG.1, in accordance with an embodiment. Generally, the etch chamber 901comprises a capacitively coupled plasma source to implement the ionmilling operations and e-beam source to implement the etching operationand to implement the optional deposition operation. As shown in FIG. 9A,a capacitive discharge is provided substantially as described elsewhereherein with the first showerhead 625 disposed above the chuck 650 todistribute a first feed gas 690 into the first chamber region 684. Thechuck 660 and the first showerhead 625 form a first RF coupled electrodepair to capacitively discharge the RF plasma 670 of the first feed gas(e.g., Ar).

FIG. 9B illustrates a cross-sectional view of the etch chamber 901reconfigured to perform the etching operation 120 illustrated in FIG. 1,in accordance with an embodiment. As shown, a high voltage DC supply 943is coupled to the secondary electrode 605 and the second showerhead 610to form a pair of DC electrodes disposed above the first showerhead 625to generate a DC glow discharge 618 in the chamber region between the DCelectrodes. The pair of DC electrodes are electrically insulated fromthe first showerhead 625 by the dielectric spacer 620. The firstshowerhead 625 is further isolated from the chamber wall 640 by thedielectric spacer 630 to permit control of the first showerhead 625.

During operation, the secondary electrode 605 is biased at a cathodic DCpotential, for example 4-8 kV while the second showerhead 610 is biasedat an anodic potential (e.g., −100V to −200 V). Electrons from the DCglow discharge 618 generated from a first feed gas (e.g., Ar bottle 690)pass through apertures 680 in into the second chamber region 681. Thefirst showerhead 625 is also coupled to a DC supply, for example to thesecond showerhead 610 via a relay, to be biased negatively to an anodicpotential relative to the cathodic potential of the secondary electrode605. The negative bias on the first showerhead 625 allows electrons topass through the first showerhead 625 and into the first chamber region684. The first showerhead 625 may have large holes for to furtheradvance this purpose. In this manner, an “e-beam” source is a means tosoftly ionize a feed gas (e.g., NF₃ and NH₃ provided by aperture 683 ina DZSH embodiment) in the first chamber region 684 to provide a reactiveetching species (e.g., NH₄F, etc.) without significant bias on theworkpiece 302.

As further depicted in FIG. 9B, while the chuck 660 is coupled to an RFsource (generators 652 and 653) during an ion milling mode, the chuck660 may also be maintained at ground potential or a cathodic potentialduring either or both the etching and deposition operations. Acontrollable, variable chuck potential 963 is provided between groundpotential and a positive bias is to control electron flux from the DCglow discharge 618 to the workpiece 302. In a further embodiment, theetch chamber 901 includes a thief electrode 947 disposed between thefirst showerhead 625 and the chuck 660. The thief electrode 625 iscoupled to ground through a variable capacitor 964 to further controlelectron flux to the workpiece 305. As shown, the thief electrode 947 isa conductive ring isolated from the first showerhead 625 by a firstdielectric spacer 630 and isolated from the grounded chamber wall 640 bya second dielectric spacer 937.

FIG. 9C illustrates a cross-sectional view of the etch chamber 901reconfigured to perform the deposition operation 130 illustrated in FIG.1, in accordance with an embodiment. Either the DC source employed forthe etching operation 120 or a second RF plasma generated in the secondchamber region 681, substantially as described elsewhere herein, isemployed to perform a PECVD deposition of the protection layer. Wherethe DC source is utilized, electrons emanating from the secondshowerhead 610 pass through the first showerhead 625 and asilicon-containing precursor, such as OMCTS 695 is provided via theapertures 683. Oxygen may also be supplied by the apertures 683 to beionized by the electron flux.

The controller 420 is to alternately energize the first plasma 670 andDC glow discharge 618 during the etching process by alternately poweringthe two sources automatically. The controller 420 may similarly placethe chamber 901 into the deposition mode.

In a further embodiment, in-situ cure of the deposited protection layermay be performed with the electron flux, essentially performing ane-beam cure-type process. The controllable, variable chuck potential 963provided between ground potential and a positive bias may controlelectron flux from the DC glow discharge 618 to the workpiece 302 forthis purpose as well. Specifically, where curing is desired, theworkpiece 302 is to be placed at ground potential and where curing isnot desired, the workpiece 302 is to be placed at a cathodic potential.

FIG. 10 illustrates a cross-sectional view of an etch chamber 1001configured to perform the various modes of the etch process 100illustrated in FIG. 1, in accordance with an embodiment. Generally, theetch chamber 1001 comprises a CCP to implement the ion millingoperations and inductively coupled plasma source (IPS) to implement theetching operation and to implement the optional deposition operation.

As shown in FIG. 10, all the chamber components previously described inthe context of the CCP plasma for the modification operation 110(FIG. 1) in the first chamber region 684 are provided, again with thechuck 660 and the first showerhead 625 forming an RF electrode pair. Inan embodiment the first showerhead 625 is a DZSH that may be powered,electrically floating, or grounded substantially as described elsewhereherein. For the etch operation (e.g., 120 in FIG. 1), the set ofconductive coils 1052 are coupled to an RF source including thegenerator 608, to generate an inductively coupled plasma 692 in anymanner known in the art. The ICP source in combination with the largesize holes in DZSH embodiments of the first showerhead enable efficientionization of feed gas, such as NF₃ 691 and NH₃ 692, introduced throughthe dielectric lid 1006.

The controller 420 is to alternately energize the first plasma 670 andICP plasma 692 during the etching process by alternately powering thetwo sources automatically. The controller 420 may similarly place thechamber 1001 into a deposition mode.

It is to be understood that the above description is intended to beillustrative, and not restrictive. Furthermore, many embodiments otherthan those described in detail will be apparent to those of skill in theart upon reading and understanding the above description. Although thepresent invention has been described with reference to specificexemplary embodiments, it will be recognized that the invention is notlimited to the embodiments described, but can be practiced withmodification and alteration within the spirit and scope of the appendedclaims. The scope of the invention should, therefore, be determined withreference to the appended claims, along with the full scope ofequivalents to which such claims are entitled.

What is claimed is:
 1. A plasma etch chamber, comprising: a chuck tosupport a workpiece during an etching process; a first showerheaddisposed above the chuck to distribute a first feed gas into the firstchamber region, wherein the chuck and the first showerhead form a firstRF coupled electrode pair to capacitively energize a first plasma of thefirst feed gas within a first chamber region between the firstshowerhead and the chuck; a secondary electrode disposed above the firstshowerhead, opposite the chuck, wherein the secondary electrode and thefirst showerhead form a second RF coupled electrode pair to capacitivelydischarge a second plasma of a second feed gas within a second chamberregion between the first showerhead and the secondary electrode; and acontroller to alternately energize the first and second plasmas duringthe etching process by alternately powering the first and second RFcoupled electrode pairs automatically.
 2. The plasma etch chamber ofclaim 1, wherein the secondary electrode is a second showerhead todistribute the first and second feed gases into the second chamberregion, and wherein the first showerhead is further to conduct the firstfeed gas or a reactive species from the second plasma to the firstchamber region.
 3. The plasma etch chamber of claim 1, wherein the firstshowerhead is coupled to a ground plane and wherein the chuck and thesecondary electrode are each coupled to an RF power source comprisingone or more RF generators.
 4. The plasma etch chamber of claim 3,wherein the chuck and the secondary electrode are both coupled to a sameRF power source through a relay switchable by the controller.
 5. Theplasma etch chamber of claim 3, wherein the chuck is coupled to a firstRF power source comprising one or more RF generators, and wherein thefirst showerhead is selectably coupled through a relay to both theground plane and to a second RF power source comprising one or more RFgenerators operable at a frequency other than that of the first RF powersource, the relay controllable by the controller.
 6. The plasma etchchamber of claim 5, further comprising a first dielectric ringelectrically insulating the first showerhead from the secondaryelectrode and a second dielectric ring electrically insulating the firstshowerhead from a ground chamber wall surrounding the chuck.
 7. Theplasma etch chamber of claim 1, wherein the chuck is movable in adirection normal to the first showerhead or the chuck includes a lifterto elevate the workpiece off the chuck to control heating of theworkpiece by the first showerhead during the etch process.
 8. The plasmaetch chamber of claim 1, wherein the first showerhead is a dual zoneshowerhead having a first plurality of aperture which fluidly couple thefirst and second chamber regions, and a second plurality of apertureswhich fluidly couple the first chamber region to a fluid source isolatedfrom the second chamber region.
 9. The plasma etch chamber of claim 1,further comprising at least one turbo molecular pump coupled to thefirst chamber region and disposed below the chuck, opposite the firstshowerhead.
 10. The plasma etch chamber of claim 9, wherein the chuck iscantilevered from a chamber wall with a single turbo molecular pumphaving a center aligned with a center of the chuck.
 11. A plasma etchchamber, comprising: a chuck to support a workpiece during an etchingprocess; a first showerhead disposed above the chuck to distribute afirst feed gas into the first chamber region, wherein the chuck and thefirst showerhead form a first RF coupled electrode pair to capacitivelydischarge a first plasma of the first feed gas within a first chamberregion between the first showerhead and the chuck and to provide an RFbias potential on the chuck; a remote RF plasma source disposed abovethe first showerhead, opposite the chuck, wherein the remote RF plasmasource is to discharge a second plasma of a second feed gas within theremote plasma source without providing an RF bias potential on thechuck; and a controller to alternately energize the first and secondplasmas during the etching process by alternately powering the first RFcoupled electrode pair and the remote RF plasma source automatically.12. The plasma etch chamber of claim 11, wherein the chuck and theremote plasma source are each coupled to an RF power source comprisingone or more RF generators.
 13. The plasma etch chamber of claim 12,wherein the chuck is coupled to a first RF power source comprising oneor more RF generators, and wherein the first showerhead is coupled to asecond RF power source comprising one or more RF generators operable ata frequency other than that of the first RF power source, the firstshowerhead isolated from a grounded chamber wall by a dielectric spacerto be electrically floating relative to the chamber wall.
 14. The plasmaetch chamber of claim 13, wherein the first showerhead and the remote RFplasma source are both coupled to the second RF power source through arelay controllable by the controller.
 15. The plasma etch chamber ofclaim 11, further comprising a second showerhead disposed between theremote RF plasma source and the first showerhead, the second showerheadto distribute etching species generated by the RF plasma source.
 16. Theplasma etch chamber of claim 11, wherein the first showerhead is a dualzone showerhead having a first plurality of apertures which fluidlycouple the first chamber region and the remote plasma source, and asecond plurality of apertures which fluidly couple the first chamberregion to a fluid source isolated from the remote plasma source.
 17. Theplasma etch chamber of claim 11, further comprising at least one turbomolecular pump coupled to the first chamber region and disposed belowthe chuck, opposite the first showerhead.
 18. The plasma etch chamber ofclaim 17, wherein the chuck is cantilevered from a chamber wall with asingle turbo molecular pump having a center aligned with a center of thechuck.
 19. The plasma etch chamber of claim 11, wherein the chuck ismovable in a direction normal to the first showerhead or the chuckincludes a lifter to elevate the workpiece off the chuck, to controlheating of the workpiece by the first showerhead to differentpredetermined amounts during the etch process.
 20. A plasma etchchamber, comprising: a chuck to support a workpiece during an etchingprocess; a first showerhead disposed above the chuck to distribute afirst feed gas into the first chamber region, wherein the chuck and thefirst showerhead form a first RF coupled electrode pair to capacitivelydischarge an RF plasma of the first feed gas within a first chamberregion between the first showerhead and the chuck and to provide an RFbias potential on the chuck; a high voltage DC supply coupled to a pairof electrodes disposed above the first showerhead to generate a DCplasma discharge, the pair of electrodes electrically insulated from thefirst showerhead by a dielectric spacer, wherein the first showerhead isbiased negatively to an anodic potential relative a cathode of the DCsupply coupled electrodes; and a controller to alternately energize theRF and DC plasmas during the etching process by alternately powering thefirst RF coupled electrode pair and the DC supply coupled electrode pairautomatically.
 21. The plasma etch chamber of claim 20, wherein an anodeof the DC supply coupled electrodes is a second showerhead havingapertures to pass electrons from the DC plasma discharge, and whereinthe first showerhead is further to conduct the first feed gas or to passthe electrons to the first chamber region.
 22. The plasma etch chamberof claim 20, wherein the chuck is has a controllable DC potentialbetween ground potential and a positive bias to control electron fluxfrom the DC plasma to the workpiece.
 23. The plasma etch chamber ofclaim 22, further comprising a thief electrode disposed between thefirst showerhead and the chuck, wherein the thief electrode is groundedthrough a variable capacitor to control electron flux from the DC plasmato the workpiece.
 24. The plasma etch chamber of claim 23, wherein thethief electrode comprises a conductive ring isolated from the firstshowerhead by a first dielectric spacer and isolated from a groundedchamber wall by a second dielectric spacer.
 25. The plasma etch chamberof claim 20, wherein the first showerhead is a dual zone showerheadhaving a first plurality of apertures which are to pass electrons fromthe DC plasma discharge, and a second plurality of apertures whichfluidly couple the first chamber region to a fluid source isolated fromthe DC plasma discharge.
 26. The plasma etch chamber of claim 20,wherein the chuck is movable in a direction normal to the firstshowerhead to control heating of the workpiece by the first showerheadduring the etch process.
 27. The plasma etch chamber of claim 20,further comprising at least one turbo molecular pump coupled to thefirst chamber region and disposed below the chuck, opposite the firstshowerhead.
 28. The plasma etch chamber of claim 27, wherein the chuckis cantilevered from a chamber wall with a single turbo molecular pumphaving a center aligned with a center of the chuck.
 29. A plasma etchchamber, comprising: a chuck to support a workpiece during an etchingprocess; a first showerhead disposed above the chuck to distribute afirst feed gas into the first chamber region, wherein the chuck and thefirst showerhead form a first RF coupled electrode pair to capacitivelydischarge an RF plasma of the first feed gas within a first chamberregion between the first showerhead and the chuck and to provide an RFbias potential on the chuck; a conductive coil disposed above adielectric chamber lid of the etch chamber and coupled to an RF sourceto generate an inductively coupled plasma discharge in a second chamberregion disposed between the dielectric chamber lid and the firstshowerhead; and a controller to alternately energize the capacitivelycoupled and inductively coupled plasmas during the etching process byalternately powering the first RF coupled electrode pair and theconductive coil automatically.
 30. The plasma etch chamber of claim 29,wherein the first showerhead is a dual zone showerhead having a firstplurality of apertures which are to pass reactive species from thesecond chamber region to the first chamber region, and a secondplurality of apertures which fluidly couple the first chamber region toa fluid source isolated from the second chamber region.
 31. The plasmaetch chamber of claim 29, wherein the chuck is coupled to a first RFpower source comprising one or more RF generators, and wherein the firstshowerhead is coupled to a second RF power source comprising one or moreRF generators operable at a frequency other than that of the first RFpower source, the first showerhead isolated from a grounded chamber wallby a dielectric spacer to be electrically floating relative to thechamber wall.
 32. The plasma etch chamber of claim 29, wherein the chuckis movable in a direction normal to the first showerhead to controlheating of the workpiece by the first showerhead during the etchprocess.
 33. The plasma etch chamber of claim 29, further comprising atleast one turbo molecular pump coupled to the first chamber region anddisposed below the chuck, opposite the first showerhead.
 34. The plasmaetch chamber of claim 29, wherein the chuck is cantilevered from achamber wall with a single turbo molecular pump having a center alignedwith a center of the chuck.
 35. A method of etching a low-k dielectricfilm, the method comprising: loading a workpiece into an etch chamber;modifying a top thickness of the low-k dielectric film disposed on theworkpiece by bombarding the workpiece with a low energy flux ofnon-reactive ions from a capacitively coupled plasma of a first sourcegas energized within a first chamber region; etching the modified topthickness of the low-k dielectric film selectively over the low-kdielectric film disposed under the top thickness by exposing theworkpiece to a reactive species generated by a plasma of a second sourcegas energized in a second region of the chamber; cyclically repeatingboth the modifying and etching until an etch process terminationcriteria is met; and unloading the workpiece from the etch chamber. 36.The method of claim 35, wherein the low-k dielectric comprises carbonand wherein the modifying comprises reducing the carbon content withinthe top thickness of the low-k dielectric film.
 37. The method of claim35, wherein the first chamber region is between a chuck supporting theworkpiece and a first showerhead, and wherein the second chamber regionis disposed above the showerhead, opposite the chuck.
 38. The method ofclaim 37, wherein the capacitive coupled plasma is generated by drivingthe chuck with an RF source to provide the workpiece with an RF biaspotential.
 39. The method of claim 38, wherein the plasma of the secondsource gas comprises a capacitive RF discharge, a DC discharge, or aninductive RF discharge.
 40. The method of claim 35, further comprisingdepositing a protection layer on an etched sidewall of the low-kdielectric film by generating a oxidizing plasma from of a third sourcegas within the second chamber region and reacting a silicon-containingprecursor with a reactive species from the oxidizing plasma within thefirst chamber region.
 41. The method of claim 40, wherein depositing theprotection layer further comprises depositing a carbon-doped siliconoxide on the workpiece periodically after a predetermined number ofmodifying and etching cycles.
 42. The method of claim 35, wherein thefirst source gas includes at least one of argon, neon, xenon, helium,and wherein the second source gas comprises at least NF₃ and a hydrogensource.
 43. The method of claim 39, wherein the workpiece is controlledto a predetermined elevated temperature of at least 80° C. during theetching.
 44. The method of claim 43, wherein the workpiece is maintainedat the predetermined elevated temperature during the entire etchprocess.